Why can't I reference a global variable defined in a class?

Question

class MyClass(object):
   code_mapping = {...}

 def get_name(code):

    code = code_mapping[code]
    ...

In this piece of code, it complains that 'code_mapping is not defined'. Isn't code_mapping is accessible to everything within MyClass?

Answer 1

Initialize it with self. This will make it accessible by any function in the class by passing it with self.<variable> and then passing self as a function argument to anything you want to pass the variable to.

class MyClass(object):
    def __init__(self):
        self.code_mapping = {...} # if this will be a hard coded 

    def get_name(self):

        code = self.code_mapping[code]
        ...

Or you could do:

class MyClass(object):
    def __init__(self, code_mapping):
        self.code_mapping = code_mapping

    def get_name(self):

        code = self.code_mapping[code]
        ...

if you'd like to pass some code mapping as an argument to your class at its instantiation.

To create a class object from this where you want {'code1' : 'name'} you then initiate a class object like this:

code1 = MyClass({'code1' : 'name'})

And then {'code1' : 'name'} will be what is carried forth into whatever get_name() does and the value of code in get_name will be name.